A 75 g Frisbee is thrown from a point 1.1 m above the ground with a speed of 12 m/s. When it has reached a height of 2.1 m, its speed is 10.5 m/s. What was the reduction in Emec of the Frisbee-Earth system because of air drag?
Chapter 20: Galaxies and the Foundation of Modern Cosmology Island of Stars o How are the lives of galaxies connected with the history of the universe 100 billion galaxies Cosmology- the study of the structure of galaxies o What are the three major types of galaxies Spiral Galaxy Has a disk with spiral arms, a central bulge, and a halo Barred Spiral Galaxy: has a bar across the middle o Lenticular Galaxy Intermediate between Elliptical and spiral galaxy Elliptical Galaxy Older, smaller stars No disk, random rotation of stars Big ball of stars, very little dust or gas No stars forming Irregular Galaxies Young galaxies Bunch of stars gravitational bound together Blue white o How are galaxies grouped together They are grouped in between whether they are spiral or more disk like. Spiral galaxies are often found in groups Clusters of galaxies Measuring Galactic Distances o How do we measure the distances to galaxies First determine the size of the solar system using radar. Use parallax to determine distances of nearby stars Use a standard candle (Object that we know the luminosity without knowing the distance) to measure the distance of further star clusters. White Dwarf Supernovae, and Cepheid variables can be used as a standard candle o How did Hubble prove that galaxies lie beyond the Milky way Hubble uses the Cepheid variables to show that other galaxies are far away. o What is Hubble’s Law Galaxies are moving away from us, and they are redshifted. Faster moving away, the further away they are Find distance using redshifts The age of the Universe o How does Hubble’s Law tell us the age of the universe The expansion rate appears same everywhere The universe had no center and no edge. Cosmological Principle The universe looks about the same no matter where you are in it. Cosmological Horizon Horizon in time not distance We cannot see beyond the begin of the universe